Process for hardening steel.



" JOHN w. ertnnanor WINDSOR, .vn artonrg 4 .ZEARKER, or W nn on, vaamonr.

HERO CESS FOR HARDENING STEEL.

No Drawing.

Toallwhomitmay coricera:

Be itknown that 1, JOHN W. GILBERT, a-citizen of the United States, residing at Windsor, in the county of Windsor and State'of Vermont, have invented'a new and useful Improvement in Processes for Hardening .Steel, of which the following is a specificatio My improved process for hardening steel is particularly adapted for hardening and tempering of those steel alloys now in common use, and known as high speed steel, and

it consists in certain improvements therein, as are hereinafterdescribed'andpo nted out in the annexed claims, I

It has been found in practice that certain I alloys of steelforming that quality now commonly used for cutting tools, and known as high speed steel, require aspecial treat ment to render them sufficiently tough to prevent the cracking of the tool, and at the same time secure a cutting edge-of suflicient resistance.

In carrying my 'improved process into practice, I first heat th'esteel. to be treated to a temperature of about 700 Fahrenheit by subjecting it to a. heating medium but little, if any, above the desired heat to which the steel is to be brought, thereby causing the heatdifi'usion to takeplace slowly. When the steel has reached a de- 7 gree of approximately 700 Fahrenheit, Iv

subject it to a heating medium of, greater intensity t'o'cause the heating to take place with greater rapidity until the steel reaches a temperature of about 1500 Fahrenheit;

The steel is then brought with greater rapidity to atemperature of from 2000 to 2500;Fa hrenheit. 4 I y -,i By the above process, the heating of-th'e steel is-accomplished progressively, and I secure this result byplacmgthe steel suecessively in furnaces of .diiferenttemper atures, or by moving it in the same furnace from one position to another, succes-. sive positlons' having greater heat intensity,

I next cool the heated steel in a metal bath heated to between 700 and 1500"v Fahrenheit. The heated steel is retained in the metal bath until it hasi'reache'd ithetem- 'perature of the bath. It is then withdrawn and cooled in the-airto atemperature less than 200 Fahrenheit; .The temper is then drawn in a ba'th' preferably of melted tallow of atemperature ranging on of Letters Patent.

hpplicationfiled 8;, 19 16. Serial No. 96,043'

Patented which the-steel is to be ot-tlie article tempered.

I am awarethat in some processes of tempering steel, metal baths, such as alumi ssrenoa OFON'E-HALF'JI'O 13mm 11.- I

Aug.i3,1918,

lfrom 500 upward "Fahrenheit, this temperatl ire dependingupon the purpose for ,used, v and the" size num', lead, or tin baths, have been used,"

and I do not thereforeelaim "broadly the use of a metal bath. r

In carry ng my process into practice I.

-' prefer to use a metal bath of'melted lead heated abovethe temperature of the meltfies ingv point, and the steel is immersed in this 1 bath until it acquires substantially the temperature. of the bath, whichsufficiently w hardens the steelwithoutcracking it.

q I am aware that steel has been treated" my process the immersion in the lead-bath becomes a cooling process owing to theh-ighby heating it to a cherry red and immersing it in a bath. of melted lead or'tin.- Bytemperature at which the steel is preheated,v

[ and the lead bath is superior-to other cooling baths now 111' useowing to'its greaterconductivity I amalso aware that-it has been a common practice'to hardensteel'by heatingand rapidly cooling it,'and to finally draw the temper by immersing the steel Pin a batlnof oil.

In the use of what are known. as high speed steels containing tungsten or other v alloy, there is great liability'of cracking, and it is difficailt to obtain the; necessary hardness combined withfthe requird 'tough- 0 ness which is securedby my process.

,The variations in temperature noted in;

the several steps of my process are deter? mined by the quality of the 'steeluand the character of the article to betreated, andthe use for which it is designed.'-

Iclaim, 1'. The process of treating-high speed steel, comprising slowly heating the steel to a temperature of about 700 Fahrenheit, 1

then heating the, steel at a more rapid rate to approximately 1500" Fahrenheit, then heating the steel. at a still more rapid. rate to-a maximum of 2000 to 2500". l lahren-f lie-it, cooling in a metali ibath to between;

Fahrenheit, increas ingin ainetal bath to between 700? and f -1500? Fahrenheit, and air cooling to approximately r00; temperature.

3. Th'e Within described method of treating 1 high speed "steel, comprising progress'ivjely heating the'ste'el to a maximum tem-' Witnesses:

mersing in a metal hath. heat eci to 700 t e 1500 Fahrenheit until the steel reaches the 'temperature. of the bath; air copling the steel and drawing it to the temper de sired in an olea-ginous bath. Dated, this third day of May 1916'. v

' J OHN W. GILBERT.

H. A. VVILLIAMS, -GLENN C..HO WLAND.I 

